1. Field Of the Invention
The present invention generally relates to a cable hanger and, in particular, relates to one such cable hanger including a pair of locking members each having an outwardly facing concave cross-section for establishing multiple point contact for retaining the cable hanger to a support structure.
2. Description of the Prior Art
Cable hangers, or clamps, have been in use for many years. Typically, such cable hangers are used to attach a cable to a supporting structure, for example, a tower. The use of supporting structures for antenna, or the like, has been known for many years. However, with the advancement and increased use of communications technology, such as cellular telephone systems, the use of towers and other support structures has increased significantly. In general, in order to ensure line of sight communications among the various antenna of a communications system, towers must be of considerable height. Because of the general safety considerations as well as the time and expense involved with installing such systems, it is highly desirable to minimize both the amount of time and the complexity of the work required for running cables along support structures. Consequently, cable hangers that can be used to rapidly attached cables to support structures without the need for conventional hardware, such as bolts, washers, nuts, or other small parts, have been developed.
In order to accommodate such cable hangers, the manufacturers of support structures provide fairly standardized cable attachment openings in various members, usually cross members, of such support structures during the manufacturing process. Typically, such attachment openings are formed to a nominal diameter of 3/4 inch and are formed in the structural member, for example, by drilling or punching, prior to a final finishing, or galvanizing, process. Such structural members have a nominal thickness of 1/8 inch. It has been found, however, that although the attachment openings have a nominal diameter of 3/4 inch, variations can occur in the surface finishing process that can result in difficulties for attaching conventional cable hangers thereto. For example, excess or irregular galvanizing can result in bubbles or irregular protuberances that extend either from the surface of the support member about the attachment opening or extend into the attachment openings. Another difficulty of such attachment openings is that there can be significant variations in the chamfer of the attachment openings, the chamfer being generally dependent upon the sharpness of the tool or die used to form the attachment openings in the support member.
One known specialized cable hanger is shown and described in U.S. Pat. No. 4,763,132, entitled Resilient One Piece Waveguide Hanger Interlockable With Antenna Tower, issued to Juds et at. on Aug. 9, 1988. The specialized cable hanger contemplated therein is designed for use only with cables that have an elliptical cross-section. Characteristic of this specialized cable hanger is the incorporation of a pair of finger-like prongs for attachment to a tower, or support structure. As described therein, each of the finger-like prongs is provided with a single outwardly extending detent. The finger-like prongs are generally semicircular in cross-section with the outboard side being curved to about the same radius of curvature as the attachment opening. In operation, the finger-like prongs are compressed and inserted through the attachment opening. Upon release of the compression force, the finger-like prongs expand such that the two detents contact the inner surface of the support member and the outboard surface of the finger-like prongs contact the inside of the attachment opening.
The finger-like prongs are designed to be urged toward the inside surface of the attachment openings and the two detents are designed to abut the inner surface of the support member about the attachment openings. The cable hanger further includes a plurality of feet that exert a spring force against the outer surface of the support member about the attachment opening. The feet thus urge the two detents against the inner surface of the support member and thereby retain the cable hanger, and the cable, to the support member.
Such an arrangement, has some drawbacks. For example, because of variations in the finishing of the attachment openings, the outboard surfaces of the prongs of the prior art specialized cable hanger may not be securely located within the inside surface of the attachment opening. For example, the presence of a non-uniformity, such as a bubble, in the galvanizing finish of the attachment opening can result in the outboard surfaces of the finger-like prongs contacting only the bubble surface rather than the inside surface of the attachment opening. Consequently, the detent associated with that finger-like prong would not fully contact the inner surface of the support member. Further, such bubbles, or protuberances can occur on the inner surface of the support member about the attachment opening as well and thereby prevent one or both of the detents from making full contact with the inner surface of the support member.
Another drawback occurs when the contact surfaces of the two detents do not fully abut the inner surface of the support member about the attachment opening. This can occur because of variations in the chamfer of the attachment openings. These conditions can cause the cable hanger to slip free of the attachment opening. Such slippage could thus allow the cable to become loose at one or more points along the length of the cable and result in deterioration of the cable and thus the communication service. Further, such an occurrence would require immediate attention which could be hazardous, time consuming and expensive. In some systems it may be desireable for a plurality of cables to be installed in a non-interfering manner along the same support structure. Such a system is shown and described in U.S. Pat. No. 4,813,639 entitled Cluster Mounting System For Supporting Coaxial Cables And The Like, issued to Midkiff et at. on Mar. 21, 1989. Therein, a mounting bracket arrangement includes a plurality of flat surfaces. Each flat surface is provided with an attachment opening through which a cable hanger may be attached.
Such a system is nonetheless subject to the above-recited difficulties since the bracket is, in essence, merely another form of a support member.
Consequently, it is highly desirable and of considerable interest to the telecommunication community to provide hence a cable hanger that provides, inter alia, a consistent, secure attachment to a support structure.